Augmented reality system controlled by probe position

A method of controlling an image guided system used in a defined three-dimensional visualization region, said system including a data processing apparatus for generating images of a subject in co-registration with the subject, a display for displaying the images to a user, a probe, and a tracking unit for tracking the location of the probe and transmitting that location to the data processing apparatus, said method comprising:

• interacting with the image guided system in a display mode when the probe is within the visualization region, wherein images of the subject are displayed in a main display region;
• and
• interacting with the image guided system in a control mode when the probe is out of the visualization region but within a defined three-dimensional interface region;
• wherein, when the probe is within the interface region the data processing apparatus obtains the position of the probe, ceases to generate the co-registered images, and generates in the main display area an image of an icon representing the probe and one or more virtual buttons, each of the virtual buttons being associated with a corresponding instruction to the system,
• wherein the user selects one of said buttons by positioning the physical probe in 3D space so as to position the representative icon relative to the apparent position of the button, and wherein the data processing apparatus sets or modifies display parameters for said display mode in response to the instruction corresponding to the selected button.